During the past 40 years there has been a remarkable decline in the prevalence of dental caries in children and adults due to the widespread use of fluoride in public health programs, such as communal water fluoridation, dental practice and in oral hygiene products. In spite of this dramatic improvement, dental caries continues to be the most prevalent dental disease. The early detection and monitoring of tooth surface demineralization is a critical step in reducing the prevalence of dental caries. The identification and validation and then use of new technologies should increase the efficiency of caries clinical trials and reduce their cost. One of the major goals of this grant is to validate new and refined technologies for the clinical assessment of tooth surface demineralization. This proposal will concentrate on using Quantitative light-induced fluorescence (QLF) alone, in combination with Red Fluorescence, and with the incorporation of a new hand piece and drying procedure. These technologies are designed to detect early signs of demineralization and should be able to monitor lesion progression and/or regression. This grant will also use the recently developed International Caries Detection and Assessment System (ICDAS) for the visual exam and record both cavitated and non-cavitated lesions. This grant will take advantage of the working relationship developed between three established teams of Cariologists during their previous program project grant and the experiences gained from that endeavor. As such the aims of this grant will include both in vitro studies (Iowa) to monitor demin/remin as well as in vivo studies (Indian and Texas) to validate monitoring of demin/remin clinically. The data generated will then be used in the fourth specific aim to develop a guide for clinical decision making that include the QLF measurements and the ICDAS visual exam. The clinical validation studies will use an Orthodontic population for permanent caries (SA 3) and a child population for deciduous caries (SA 2). The "exfoliated tooth model histopathology" will be used with the studies on the deciduous dentition as the gold standard for validation. The clinical data will be paired with the PLM for validity measurements and analyzed by the biostatisticians.